Answer:
D: 4.6 x 
Explanation:
4.6 x 10^{9} = 4,600,000,000
Earth is approximately, 4.6 billion = 4,600,000,000 = 4.6 x 10^{9}
Reaction which breaks down complex molecules into simpler ones n release energy
Scientists use fossils to study earth history by identifying the fossil and what era it came from. By knowing what era the fossil came from and what location it was found, scientists can make assumptions about the earth formation at that time.